Measurement instrument for testing charge storage devices

ABSTRACT

A test instrument for use with a sample having a plurality of electrically conducting contact pads, the instrument including: a controllable, variable force linear actuator; a probe assembly operated by the linear actuator, the probe assembly having a probe head at one end with a surface for contacting the sample; a movable contactor assembly including a plurality of contacts for electrically contacting the plurality of contact pads on the sample; a housing on which the linear actuator and contactor assembly are mounted, the housing having an identified area for holding the sample during testing; a position sensor assembly for measuring changes in the position of the probe; and a sensor for measuring a force applied to the sample by the probe head.

This application claims the benefit under 35 U.S.C. §119(e) ofProvisional Application Ser. No. 62/028,431 filed Jul. 24, 2014,entitled “A Measurement Instrument for Testing Charge Storage Devices,”the entire contents of which are incorporated herein by reference.

TECHNICAL FIELD

This invention generally relates to test instruments and relatedequipment for measuring and for electrically and mechanicallycharacterizing test devices such as actuators, batteries, capacitors,supercapacitors, ultracapacitors, hybrid capacitors, pseudocapacitors,biological samples, dielectrics, gels, liquids, solids, etc.

BACKGROUND

The development of high energy density storage devices can be alaborious and time consuming process. A typical energy storage devicemight include a first polymer electrode, a second electrode inelectrochemical communication with the first electrode, a separatormaterial between the two electrodes, and an electrolyte or other mobilephase in contact with both electrodes that can dissociate into anionsand cations. There are many different chemical materials that could beused for each of these elements. So, the number of possible ofcombinations that might need to be tested can be huge. For testing thesecombinations one has to, in essence, build a representative device foreach combination of materials and then run that device through thedesired set of tests to characterize that combination of materials.Thus, finding the best combination of materials can involve constructingand electrically testing thousands and thousands of devices representingthe many different possible combinations of materials and electrolytes.

The regimen of tests required to satisfactorily measure the electricalcharacteristics of a device might also be quite large. For example, thetests might include measuring capacitance, resistance, energy in versusenergy out, Coulombic efficiency, energy density, power density,specific energy, specific power, IR drop, IR gain, current density, etc.

SUMMARY

The embodiments described here, particularly when used in combinationwith each other, provide a rapid, efficient, consistent, and reliableway of testing test devices.

In general, in one aspect, the invention features a test instrument foruse with a sample having a plurality of electrically conducting contactpads. The instrument includes: a controllable, variable force linearactuator; a probe assembly operated by the linear actuator, the probeassembly having a probe head at one end with a surface for contactingthe sample; a movable contactor assembly including a plurality ofcontacts for electrically contacting the plurality of contact pads onthe sample; a housing on which the linear actuator and contactorassembly are mounted, the housing having an identified area for holdingthe sample during testing; a position sensor assembly for measuringchanges in the position of the probe; and a sensor for measuring a forceapplied to the sample by the probe head.

Other embodiments include one or more of the following features. Thelinear actuator is a pneumatic actuator which comprises an air bearingcylinder and the sensor for measuring the force applied to the sample bythe probe head is a pressure sensor arranged to measure a pressure ofgas applied to the pneumatic actuator. Alternatively, the linearactuator is an electromagnetic actuator and the sensor for measuring theforce applied to the sample is located on the housing at the identifiedarea where the sample is held during operation. The test instrument alsoincludes: one or more conduits proximate to and in thermal communicationwith a portion of the housing next to the identified location, the oneor more conduits for carrying temperature-controlled fluid forcontrolling a temperature of the sample during testing; and atemperature sensor for measuring a temperature of the housing near theidentified area where the sample is located during operation. Thetemperature sensor is thermistor or a resistive temperature detector.

Other embodiments also include one or more of the following features.The position sensor assembly is a non-contact, optical position sensorassembly including an optical read head and a scale with markings. Theoptical read head is mounted on the housing and the scale is mounted onthe movable probe assembly. The plurality of contacts is a plurality ofcontact pins which are spring-loaded. The test instrument also includesa heating element located on the housing near where the sample ispositioned during operation. The heating element is a Peltier device ora resistive heater element.

At least some of the embodiments described herein enable the personperforming the tests on test devices to have precise control overvarious environmental conditions under which the electrical tests areperformed. For example, the tester can, without limitation: apply acontrolled static or dynamic pressure to sample during the test;selectably control the specific static temperature at which the testsare performed; selectably control the dynamic temperature imposed on thedevice; precisely measure the linear (vertical) displacement of a loadapplying element during testing; conduct isometric tests on the sample(i.e., control position while measuring force); and conduct isotonictests on the sample (i.e., control force while measuring position).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the left side of a test instrument.

FIG. 2 shows in a partial cross-section the test instrument of FIG. 1from the right side.

FIGS. 3A and B show front of the test instrument of FIG. 1, one inpartial cross-section to more clearly reveal relevant internal features.

FIG. 4 shows a platform which is part of the test instrument shown inFIG. 1.

FIG. 5 shows an alternative probe head design.

FIG. 6 shows a sachet in its fully open position.

FIG. 7 shows the sachet of FIG. 6 in a closed configuration.

FIG. 8 is a block diagram of a test system including the test instrumentdescribed above.

DESCRIPTION

The testing system described herein includes a test instrument 100(shown in FIG. 1) and a specially designed sample holder or sachet 500(shown in FIG. 6) which fits into test instrument 100 and holds thedifferent electrochemical materials the electrical properties of whichare to be tested.

The Test Instrument

Referring to FIG. 1, test instrument 100 is capable of controlling thepressure that is applied to the sample and the temperature of the sampleduring measurement of its electrical characteristics. It is capable ofmeasuring the physical expansion of the test sample as it is beingmaintained under a constant pressure while its electricalcharacteristics are being measured. It is capable of controlling thetemperature of the test sample during those measurements. And it iscapable of measuring the pressure generated by the test sample as itsthickness is constrained to a constant value during electrical testing.

Test instrument 100 includes a machined aluminum body 102 mounted on amachined aluminum support platform 104. Body 102 provides support for alinear actuator 106 which controls the up and down movement of a probehead 108 attached to the working end of actuator 106. Actuator 106 isscrewed into the top side of body 102 with its actuator shaft 112extending down towards support platform 104. Probe head 108 is screwedonto the end of actuator shaft 112 and has a flat working surface 114 onits lowermost end which contacts the test sample (not shown) duringoperation. Actuator 106 is used to apply a controlled force/pressure toa sample (not shown) which is positioned in a flat recessed area 110 onsupporting platform 104 during testing. Care is taken to make sure thatthe longitudinal axis of actuator 106 is perpendicular to the plane ofrecessed area 110 and that working surface 114 of probe head 108 whenassembled onto the working end of actuator 106 is parallel to the flatsurface of recessed area 110. This is to assure that the force/pressurethat is applied to the test sample is uniform across the contacted areaof the sample.

In the described embodiment, the linear actuator is an AirpelAnti-Stiction® Air Bearing cylinder from Airpot Corporation. It is apneumatic actuator capable of highly accurate force control due to itslow stiction. It includes a graphite piston and a borosilicate glasscylinder with an air bearing between the piston and the glass cylinder.It is capable of responding to forces as low as only a few grams andpressures less than 0.2 psi. The force that is applied by the aircylinder is a known function of the pressure of the air supplied to thecylinder. So, by monitoring the air pressure with an inline pressure,analog output sensor, one can easily determine the force/pressure thatthe probe head applies to the test sample.

Other types of actuators could also be used, such as for example,electromagnetic Lorentz-force actuators of the type described in U.S.Pat. No. 7,833,189, entitled “Controlled Needle-Free Transport”,incorporated herein by reference. It is generally desirable, however, touse those types of actuators having low stiction given the sensitivityof the tests that likely will need to be performed. Use of precisionair-bearing cylinder has advantages over many of the alternatives. Itminimizes the frictional forces typically associated with thetraditional linear elements. The reduced friction, in turn, maximizesthe accuracy of the thickness measurement and optimizes the dynamicrange and sensitivity of the device. Also, long duration tests benefitfrom the use of pneumatic actuators, as they do not typically requireconstant energy input (i.e., power) to achieve consistent and uniformforce application. Short duration tests with high bandwidth or largedynamic range may benefit from Lorentz force actuators.

If an actuator other than the one described herein is used, the testinstrument will also need to include a separate force-sensing deviceoptionally located between the probe head and the actuator shaft.

As shown in FIG. 2, a secondary air bearing support element 116 islocated at the output end of actuator 106. This provides off axisstiffness for shaft 112 with little to no stiction to keep shaft 112precisely aligned perpendicular to the plane of recessed area 110. Atthe top of actuator 106 is an input port through which pressurized airis supplied to actuator 106. This input port has a threaded portion ontowhich the fitting on the supply line (not shown) is threaded.

Probe head 108 includes a magnetic ring 120 on its upper surfaceencircling actuator shaft 112 where it is screwed into the top of probehead 108. Also, probe head 108 includes a lift arm 122 located andextending away from its top front region. Lift arm 122 provides an easyway for the operator of test instrument 100 to manually lift probe head108 when it is necessary to ether insert a new test sample into recessedarea 110 or remove a test sample from recessed area 110 pr manuallylower probe head 108 after a test sample has been inserted. Ring magnet120 holds probe head 108 in its up position while these operations arebeing performed.

Test instrument 100 also includes an optical sensor assembly 124 mountedon body 102 at the back of and close to probe head 108. Optical sensorassembly 124 includes a read head sensor 126 which detects the markingson a scale 128 that is mounted on the back of probe head 108. In thedescribed embodiment, optical sensor assembly 124 is a TONiC™ made byRenishaw. It is a super-compact, non-contact optical encoder that offersspeeds up to 10 m/s and resolutions down to 1 nm.

By detecting movement of scale 128 which is mounted on probe head 108,optical sensor assembly 124 provides a way to accurately measure theabsolute position of probe head 108 when performing measurements on thetest sample. Thus, if the sample swells when power is being delivered tothe test sample or when it is being discharged, the precise amount ofthe swelling can be measured using optical sensor assembly 124. Inaddition, with the aid of a controller, the pressure being applied bythe probe head to the sample can be varied so as to constrain thethickness of the test sample to a constant maximum value.

Alternative sensors other than optical sensors could also be used,including for example, capacitive probe sensors and magnetic positionsensors.

Mounted on the back of body 102 is a solenoid 130 which, under externalcontrol, turns on and off the supply of air pressure to actuator 106. Ithas an input port 132 to which an air supply line (not shown) isconnected, an output port 134 to which a line (not shown) connected toinput port 118 of actuator 106 is attached, and a power input 135 foroperating the solenoid.

Referring to FIGS. 1 and 4, for purposes of temperature control,platform 104 has three flow channels 132 extending from one side to theother directly beneath recessed area 110 into which test samples areinserted for testing. At each end of each flow channel 132 is a threadedportion 134 which allows a threaded fitting (not shown) to be screwedinto the platform. On one side of platform 104, there is a recessed area136 circumscribing the opening to each channel 132. These recessed areas134 are for receiving O-ring seals (not shown). During operation of thetest instrument, heated or cooled water is flowed through these channels132 to control the temperature of platform 104 and thereby controllingthe temperature of the device resting on the platform.

Referring to FIGS. 3B and 4, platform 104 includes a channel 160 drilledin through the back and extending to a location that is between themiddle flow channel 132 and the middle of recessed area 110. Atemperature sensing device 161 (e.g. thermistor, resistance temperaturedetectors, thermo pile/IR—non contact) is positioned within channel 160at the location below recessed area 110. This device is used fortemperature sensing and control.

The design of the test instrument with particular regard to the heatingand cooling manifold assembly just described enables it to be operatedas a standalone unit or ganged together with any number of other testinstruments. Depending on how the test instrument is setup (i.e., eitheras a standalone or ganged together with other test instruments)appropriate fittings are screwed into the threaded areas at the ends offlow channels 132. If the test instrument is set up as a standaloneunit, then fittings for making connections to the water lines of thetemperature control system are screwed into the threaded portions 134.

If the test instrument is set up as part of an array, they are lined upnext to each other so that their sides abut and the flow channels are inalignment with each other. In this configuration, O-rings are insertedinto the recessed areas 136 around the flow channels 132. When one unitabuts up against a neighboring unit, the O-ring contacts the side wallof the platform of the neighboring unit and forms a seal which preventsfluid from leaking out of the manifold. The multiple units are then heldtogether by rods (not shown) with threaded ends that are inserted in thealigned holes 146 (see FIG. 1) of the multiple test instruments in thelineup. Nuts at the end of those threaded rods are tightened down toforce the units tightly together so the O-rings form good seals in theflow channels at the interfaces between neighboring units. In this way,it is possible to set up large clusters of test instruments formassively parallel testing of devices thereby enabling more rapidprototyping and experimentation on complex composite systems. Also,individual test devices can be easily added and removed.

As an alternative to the heating/cooling manifold described above, onecould instead use individual heating elements (e.g. Peltier devices orresistive heaters) that are mounted in recessed areas 110 on platform104. If that approach is used, it would be appropriate to placeinsulators between the heater elements and the platform to reduce theloss of heat to the more thermally conductive platform. In addition,temperature sensors would also be placed above the heater elements toaccurately monitor the temperature of the test device. By using theindividual heaters the speed at which the device temperature can bechanged is much higher as compared to the manifold approach in which thetemperature of the water and the platforms (representing a much higherthermal mass) needs to be changed.

For making electrical contacts to test samples in the test instrument,there is a contactor assembly 138 mounted on one side of body 102.Contactor assembly 138 includes a 2×8 array of POGO LC contactors 144attached to its bottom side. The pattern and spacing of the contactorsis identical to the pattern and spacing of the contact pads on the testsample, which is described in greater detail below. A bolt 142 whichscrews into body 102 at location 144 (see FIG. 3) provides a shaft aboutwhich contactor assembly 138 can be pivoted to raise and lower thecontactors. Extending upward from the contactor assembly is a lever arm140 which the operator uses to manually rotate the unit about the pivotestablished by bolt 142 to thereby raise and lower the contactors. Thepogo pins are appropriately preloaded by torsion springs so as toestablish good contact with the contact pads when the contactor assemblyis lowered into position.

An alternatively designed probe head 108′ is shown in FIG. 5. It has theadvantage of having a contacting surface 114′ that can easily tilt by asmall amount in any direction to thereby accommodate a sample that mightnot have a parallel top surface. This tilting ability assures a moreuniform distribution of the applied pressure over the surface of thetest sample.

The alternative probe head 108′ includes a housing 160 which encloses acontactor probe 162 having a bottom surface 114′ that contacts thesample under test. Housing 160 has a hollow region in which contactorprobe 162 is largely contained except for a small portion of the bottomportion of contactor probe 162 that extends outside of the housing (thisis the portion that contacts the test sample). At its upper end, thereis a hole that accommodates to top end of contactor probe 162. Thebottom surface 114′ of contactor probe 162 is flat and circular. Theupper end 164 of contactor probe 162 is cylindrically shaped and fitsinto the hole in housing 160. Between the flat bottom surface and thecylindrically shaped upper end, the contactor probe is conically shapedand tapers down to a narrow diameter neck and then tapers back out tothe diameter of the cylindrically-shaped upper end thereby forming arigid conical flexure region. The opening in housing 160 into whichcontactor probe fits is cylindrical, has a slightly smaller insidediameter than the diameter of the flat circular surface of probe head108′, and has a beveled edge 168 which has the same angle as the angleof the tapered portion of the probe head to which it is adjacent. Narrowconical flexure region 166 is sufficiently thin so as to enable the headto easily flex and thereby permit the probe head to tilt off axis by asufficient amount to accommodate any slight tilt in the top of thesample under test. The diameter of the narrowest portion is, however,designed to be large enough to enable the probe head to transmit themaximum force desired for testing the sample without buckling ordeforming.

The Sachet

Referring to FIG. 6, sachet or sample holder 200 is a structure thatenables one to easily assemble a cell for testing the performance of aparticular device chemistry. The materials to be tested are placed ontosample holder 500, it is folded together to form a sealed packet or cellas shown in FIG. 7, and that sealed packet is placed on the testinstrument to perform an array of electrical tests.

Sample holder 200 is constructed from a flexible, highly impermeable,hydrophobic sachet material 202 (Kapton a.k.a. polyimide, or PET/mylar)which allows for dynamic motion of the materials under test within whilepreventing contamination by external environmental elements. It has twosymmetrical portions or wings 204 a and 204 b which are separated by ahinge 206. In the described embodiment, hinge 206 is formed by a linearsequence of small holes or perforations through film 202 which rendersthe film more easily foldable along the line defined by theperforations. Except for a contact pad tab 208 on one of the wings,wings 204 a and 204 b of sample holder 200 have the same shape and sizeso that when they are folded over onto each other, they align and matchup with each other.

In the illustrated embodiment, the outer perimeter of each wing 204 aand 204 b is in the shape of a “U” with parallel opposite sides thatjoin a curved portion that represents the bottom of the “U”. The outerperimeter of the curved portion is a segment of a circle. Note that theshape and size of recessed area 110 in platform 104 of the testinstrument (see FIG. 4) is the same as that of the assembled sachet soas to hold the sachet in a precise and repeatable location for testingwith the tab properly aligned with the contactor assembly. Of course,other shapes for the sachet are also possible which accomplish the sameobjective.

On each wing 204 a and 204 b there is an annular region 210 a and 210 bthat completely circumscribes a central region and the outer perimeterof which coincides with the curved outer perimeter of the wing. Theannular regions 204 a and 204 b are arranged and sized so that theycompletely align and match up with each other when film 202 is foldedtogether about hinge 206. Applied to the entire annular region on eachwing is a pressure sensitive adhesive (PSA) covered by ring of releasematerial 212. In the described embodiment, the contact adhesive isacrylic-based 3M 467MP pressure sensitive adhesive. The ring of releasematerial paper renders the test sample more easy to handle duringassembly and prevents any foreign objects from inadvertently sticking tothe adhesive.

Alternative sealing methods can, of course, be used. For example, heatsealing through ultrasonic welding is one possibility. Or other types ofglue can be used. The choice may depend somewhat on the materials thatwill be tested within the sachet and the need for rapid assembly and thedegree to which sachet must be environmentally sealed.

Within the center of each annular region 210 a and 210 b are largecircular contact electrodes 214 a and 214 b that are coaxially alignedwith the annular region. The contact electrodes 214 a and 214 b covermost of the center region inside the annular region except for a ringregion 216 a and 216 b surrounding the contact pad and separating itfrom the annular region.

Tab 208 that extends off to the side of one of the wings 204 a includestwo parallel rows with eight contact pads 218 in each row. A wideconducting trace 220 connects four of the contact pads 218 to centralcontact electrode 214 a and another wide conducting trace 222 connectsfour other contact pads 218 to central contact electrode 214 b. Inaddition to the wide conducting traces 220 and 222, there are two narrowconducting traces 224 and 226, one connecting a contact pad 208 toelectrode 214 a and another connecting another contact pad 218 toelectrode 214 b. The wide conducting traces 220 and 222 are forsupplying power to electrodes 214 a and 214 b, which is why thoseconducting traces are wide. Since they will carry larger currents, theirresistances need to be low to avoid causing excessive voltage drops andheating between the contact pads 218 and the electrodes 214 a and 214 b.The narrow conducting traces 224 and 226 serve as sensing traces formeasuring the voltages of the corresponding electrodes. Since they willcarry very little current, there will be no appreciable voltage drop andthey can therefore be narrower.

The unused contact pads, which equal six in number in the illustratedembodiment, can be used to connect to other embedded sensors within thedevice structure that one might wish to include. For that purpose, inthe described example, two contact areas 230 and 232 are included inring 216 a and one contact area 234 is included in ring 216 b. Thesecontact areas are, in turn, connected to corresponding pads on tab 208via electrically conducting traces. The contact areas in the open areasof the two rings 216 a and 216 b provide points to which other embeddedsensors can be connected. By using such pre-wired reference electrodetraces one can: attach various reference elements (e.g. silver,platinum, gold, copper, etc.); construct many varieties of sample types;and implement various electrochemical test protocols/procedures (e.g.cyclic voltammetry, galvanostatic measurement, potentiostaticmeasurement, impedance spectroscopy, etc.) using the same testapparatus, electronics, and sachet. For example, it is possible tomeasure sachet temperature by resistive measurement of a calibratedtrace, in which case two of the contact pads 218 on tab 208 would beused to connect to the two ends of the calibrated trace.

When the assembled sachet, with the test material inside the sealedpacket, is inserted into the test instrument, tab 208 and the contactpads 218 align with the contactors 144 on the contactor arm assembly 138of the test instrument thereby allowing external test circuitry tocommunicate with the test device and any sensors that are incorporatedinto the test device.

In the described embodiment, the electrodes and leads are madeelectrolytic copper, plated with electroless nickel and thenelectroplated with a low resistance, low corrosion, low contamination,high purity soft-gold. The metal areas can be fabricated by using any ofa number of different, well known techniques. For example, they can befabricated by using ENIG (the Electroless Nickel Immersion Goldprocess). Or one could use soft gold electroplating. Both of thosetechniques involve a gold layer formed on a nickel layer.

Alternatively, the contacts could be fabricated from other metals suchas aluminum. The choice of material may depend upon the chemistry of thematerials that are to be put in the sachet for testing, some materialsbeing more resistant to degradation and/or corrosion when exposed to aparticular chemistry than others.

Assembly of the test sample is straightforward and simple. With wings204 in their unfolded or open position, the release film is removed fromthe adhesive areas. Then, the materials to be tested are applied to oneof the electrodes. When the device structure is fully assembled, onewing is folded about the fold line onto the other to form a sealedpacket with the device contained inside. The use of the perforated foldline makes possible repeatable, rapid assembly of samples without havingto use a special jig or procedure to align electrode pads.

The sachets can be designed with the objective of minimizing thecompressive force exerted by the sealing ring on test sample material.For example, the compliance of the film, the distance from edge of theadhesive region to the electrode (or sample area), and the possibilityof including a shim washer element between the adhesive area and theelectrode are all design parameters or features that can be used toreduce or prevent undesirable non-planar distortion of the sample.

The process for fabricating the sachets uses conventional, commerciallyavailable techniques. In general, a stack of the different layers isassembled and bonded together. There is a first dielectric layer (e.g. apolyimde layer), followed by a layer of adhesive, then the layer ofconducting traces, followed by another layer of adhesive, and endingwith a final dielectric layer on top.

In the described embodiment, the sachet employs one ring of a contactadhesive on both wings to form the seal and hold the two wings together.Under some circumstances, however, this may not provide sufficientsealing, especially when exposed to certain electrolytes that might beused in the sample under test. A more secure and more permanent way ofsealing the two wings together is to use two concentric rings ofadhesive. The outer ring uses the adhesive material described above;while the inner ring uses an epoxy that takes time to cure perhaps withheat or UV. The outer ring holds the assembly together while the epoxycures. The epoxy ring protects the adhesive from being exposed to theelectrolyte and after it cures provides both a stronger bond holding thetwo wings together and one that is more resistant to degradation by theelectrolytes and also evaporation and/or oxygen or other gas permeation.

Optionally, the sachet can also include a marking coating applied to thebackside to provide an area on which the test operator can writeidentifying information and other relevant data relating to thatparticular test device.

Referring to FIG. 8, a complete system, including a test instrument 800constructed in accordance with the ideas presented herein, includes anair supply 802 (or source of pressurized gas) for operating the aircylinder in test instrument 800, a flow controller 804 which modulatesthe flow of air to the air cylinder which in turn controls the forceapplied by that air cylinder to the test sample, a pressure sensor 806for measuring the force that is applied by test instrument 800 to thetest sample, and a solenoid 808 for turning on and off the flow of gasto the test instrument 800.

The system also includes a heating/cooling system 810 for controllingthe temperature of the fluid (e.g. water) that is supplied to the testinstrument platform on which the test sample is resting during testing.

To perform the desired electrical measurements, there is a rack ofelectrical test equipment 812. This includes at least a power supply forpowering the device under test as well as other measurement instrumentsappropriate for the types of electrical measurements that are to beperformed such as, for example, device capacitance, resistance, energyin/out, Coulombic efficiency, energy density, power density, specificenergy, specific power, IR drop, IR gain, current density, etc. Theelectrical test equipment is electrically connected via wires to thecontactor assembly which, in turn, provides the electrical connectionsto the device under test.

A system controller 814 controls the operation of flow controller 804,solenoid 808, heating/cooling system 810, and electrical test equipment812. It runs the various tests, either under the manual control of anoperator or automatically under programmed control, and stores theacquired data along with the relevant operating conditions (e.g.temperature, pressure) in local memory 816.

Air supply 802, flow controller 804, pressure sensor 806, and solenoid808 make up the force controller, i.e., the subsystem that sets andcontrols the force that is applied to the test sample by the probe head.If another type of actuator is used instead of an air cylinder asdescribed herein then other components would be substituted for thesecomponents. For example, if a Lorentz-force linear actuator is used,then a variable power supply (or current supply) is substituted for theair supply and flow controller. And the force measurement might be madeby a strain gauge that is integrated into the probe assembly.

Other embodiments are within the following claims. For example, amicrocontroller and memory chips can also be included on the sachetthereby allowing for the creation of an intelligent device that may, forinstance, know its test history, its material construction, and even theuse of the data to feed back for optimal experimental implementation inmassively parallel test environment. Also, the sachet can include asepta for introducing and/or reintroducing fluid (e.g. electrolyte) intoan already assembled test sample.

What is claimed is:
 1. A test instrument for use with a sample having a plurality of electrically conducting contact pads, said instrument comprising: a controllable, variable force linear actuator; a probe assembly operated by the linear actuator, said probe assembly having a probe head at one end with a surface for contacting the sample; a movable contactor assembly including a plurality of contacts for electrically contacting the plurality of contact pads on the sample; a housing on which the linear actuator and contactor assembly are mounted, said housing having an identified area for holding the sample during testing; a position sensor assembly for measuring changes in the position of the probe; and a sensor for measuring a force applied to the sample by the probe head.
 2. The test instrument of claim 1, wherein the linear actuator is a pneumatic actuator.
 3. The test instrument of claim 2, wherein the pneumatic actuator comprises an air bearing cylinder.
 4. The test instrument of claim 3, wherein the sensor for measuring the force applied to the sample by the probe head is a pressure sensor arranged to measure a pressure of gas applied to the pneumatic actuator.
 5. The test instrument of claim 1, wherein the linear actuator is an electromagnetic actuator.
 6. The test instrument of claim 5, wherein the sensor for measuring the force applied to the sample is located on the housing at the identified area where the sample is held during operation.
 7. The test instrument of claim 1, further comprising: one or more conduits proximate to and in thermal communication with a portion of the housing next to the identified location, said one or more conduits for carrying temperature-controlled fluid for controlling a temperature of the sample during testing; and a temperature sensor for measuring a temperature of the housing near the identified area where the sample is located during operation.
 8. The test instrument of claim 7, wherein the temperature sensor is thermistor.
 9. The test instrument of claim 7, wherein the temperature sensor is a resistive temperature detector.
 10. The test instrument of claim 1, wherein the position sensor assembly is a non-contact, optical position sensor assembly comprising an optical read head and a scale with markings.
 11. The test instrument of claim 10, wherein the optical read head is mounted on the housing and the scale is mounted on the movable probe assembly.
 12. The test instrument of claim 1, wherein the plurality of contacts is a plurality of contact pins.
 13. The test instrument of claim 12, wherein the plurality of contact pins are spring-loaded.
 14. The test instrument of claim 1, further comprising a heating element located on the housing near where the sample is positioned during operation.
 15. The test instrument of claim 14, wherein the heating element is a Peltier device or a resistive heater element. 